Probably the weather has limited webworm activity this year.

In fact, I am surprised that following the early September showers there were not any webworm calls and questions. The fall webworm is a common caterpillar pest of trees.

It attacks more than 88 different kinds of plants, including many fruit, nut and ornamental trees and shrubs.

Fall webworms are known for the large, unsightly webs they produce.

Heavy infestations are rarely fatal, but if they occur repeatedly over several years they can stress trees and make them more susceptible to drought, disease or other insect pests.

The fall webworm moth is white and has a wing span of 1 to 1-1/2 inches. Sometimes there are small, dark spot on the forewings.

Full-grown larvae are approximately 1 inch long, pale green or yellow, and covered with tufts of long white and black hairs.

The webworms often cover entire branches with their webs. In extreme infestations whole trees may be covered. Larvae feed within the web, eating the tender parts of leaves while avoiding the larger veins and midrib.

Fall webworms have four generations each year in southern portions of Texas.

Female moths deposit hair-covered egg masses on the undersides of the leaves of their food plants.

Egg masses may be deposited in either a single or double layer and can contain up to 600 eggs. Each female moth will deposit only one egg mass.

The larvae begin to build a silk web soon after hatching. As larvae consume leaves within the web, they expand the web to take in more foliage.

All larvae within a web are the offspring of a single egg mass. Larvae will molt six or seven times before leaving the web to pupate. The life cycle from egg to adult requires approximately 50 days under ideal conditions.

Fall webworms often can be controlled without insecticides by removing and destroying any leaves that contain egg masses.

Larvae may be knocked out of lowhanging webs with a stick or broom and into a box or garbage bag for disposal. Webs also can be pruned from smaller branches.

If webs are too numerous or too high in a tree to deal with individually, insecticides can be used to prevent damage.

Hose-end sprayers or commercial highpressure sprayers are best for reaching upper portions of tall trees. Because webworm larvae remain inside their webbing, insecticide sprays must penetrate the web to be effective.

Insecticides containing Bacillus thuringiensis (Bt) are effective.

Insecticides containing Bt are selective for caterpillars and do not harm beneficial insects; however, they must be applied when caterpillars are small for effective control.